Tesco, Britain's biggest supermarket, has pledged to give customers a detailed
insight into its global supply chain in a bid to restore customer confidence
after the horse meat scandal.

Philip Clarke, the supermarket's chief executive, insisted a more transparent supply chain and creating "world class" traceability in the products it supplied would not lead to increases in the price of food.

It comes as the head of the Food Standards Agency admitted it is unlikely the exact number of people who have unwittingly eaten horse meat will ever be known.

Catherine Brown, chief executive of the government watchdog, which is investigating the cause of the contamination of pre-prepared beef products with horse meet, said the industry needed to act with "more transparency and engagement".

Three men who were arrested by police also investigating the horse meat mislabelling scandal have now been released on bail.

Dafydd Raw-Rees, 64, the owner of Farmbox Meats near Aberystwyth, and a 42-year-old man, were arrested in Wales on Thursday on suspicion of offences under the Fraud Act.

A 63-year-old man was also arrested on suspicion of the same offence at Peter Boddy Slaughterhouse in Todmorden, West Yorkshire.

The men have been released pending further inquiries and will return to answer bail in Aberystwyth at a later date, Dyfed Powys Police said.

Writing in a blog on the Tesco website, Mr Clarke said the supermarket was now reviewing its supply chain and intended to open up the details of it to the public.

He also said that the measures they were taking would not mean more expensive food.

He said: "I have asked my team to review our approach to the supply chain, to ensure we have visibility and transparency, and to come back with a plan to build a world class traceability and DNA testing system

"We pledge that over the weeks and months ahead, we will open up our supply chain, and give you more information than any retailer has before to enable you to make informed choices about the food you buy for your family.

"We pledge that over the weeks and months ahead, we will open up our supply chain, and give you more information than any retailer has before to enable you to make informed choices about the food you buy for your family.

"And let me be clear that this doesn’t mean more expensive food – it just means doing things the right way, and accepting nothing less than the highest possible standards in the supply chain."

He said details of the product testing programme would be posted on a new website.

His comments come as the head of another major UK supermarket chain insisted the horse meat scandal was not "the tip of an iceberg".

Justin King, chief executive of Sainsbury's told BBC's Newsnight programme that supermarkets had not been slow to react to the scandal, but conceded there was a long way to go before the food industry could fully explain how the crisis has come about.

He said: "I don't think it's the tip of an iceberg. I think there are some encouraging signs from today's tests that we are starting to get to the bottom of this particular issue.

"We, in Sainsbury's, have a huge testing programme – we have 50-odd people whose full-time jobs are to test product.

"They test raw materials when they come into the factory. The product is delivered to our warehouses and we buy product, as customers do, to test it too. And most of the industry would say something similar.

"So we go to great lengths to ensure our food is what we expect it to be. Trust is the core of our businesses."

Officials at the Food Standards Agency were continuing to examine evidence seized from three premises in England on Thursday morning.

Documents and transportation information was taken away from Dinos and Sons Continental Foods in Tottenham while further documents and meat samples were taken for testing from Flexifoods in Hull.

A lawyer for Dinos and Sons, which supplies speciality Mediterranean food, said it had transported some frozen meat for Flexifoods which had been found to contain horse meat, but had not had any other involvement with the products.

The FSA has also handed evidence to European investigators at Europol.

Catherine Brown, chief executive of the FSA, said that even as investigations continued, it would never be possible to find out how many consumers had actually eaten horse meat without realising it.

She said: "I don't think that we ever will (know how many), because these tests are a snapshot, so even where we find things it is very hard to work out how long, what number of batches, so I think it is unlikely that we will ever know that. It is shocking."

As the results were confirmed, pub and hotel group Whitbread became the latest company to admit horse DNA had been found in its food, saying their meat lasagnes and beefburgers had been affected.

The firm, which owns Premier Inn, Beefeater Grill and Brewers Fayre, said the products had been removed from their menus and will not be replaced until further testing has been carried out.

Horse meat was discovered in school dinners for the first time since the scandal began, it was also revealed.

Cottage pie testing positive for horse DNA was sent to 47 Lancashire schools before being withdrawn.

Judy Hargadon, chief executive of the Children's Food Trust, said that parents, schools and caterers in Lancashire would feel "let down".

"Whether you're a parent buying food at the supermarket or a caterer dealing with a supplier, we're all buying our food in good faith," she said.

"What the last few weeks have taught us, here in the UK and elsewhere, is that people buying in good faith have all been let down by these issues in the supply chain."

Janice Gillan, chairman of Hospital Caterers Association, said all food suppliers to hospitals would be assessed to trace the sources of their meat products.

It emerged on Friday that burgers containing horse meat have been supplied to hospitals in Northern Ireland.

Ms Gillan told BBC Breakfast: "There is no risk to patients because patient safety is our ultimate paramount. The vast majority of hospital catering is produced on site using fresh butcher meat and all our suppliers are independently assessed and audited.

"The independent assessor is currently out reassessing all our suppliers at the moment to get real assurances for the public.

"What we really need is full traceability of all meat products because we know that all animals have passports, so you can trace the animal from the birth through the food chain."

She added: "If anything shows up at all, for example the burgers in Northern Ireland, then they're immediately removed from the premises."